The present invention relates in general to audio/video equipment and in particular to a new and useful apparatus which can be used to first record and then reproduce a stereo audio signal using a monoral audio head of a video tape recorder.
Most video tape recorders (VTR's) are provided with monoral audio heads that are incapable of distinguishing between the two channels of a stereo audio signal. Since stereo signals are readily available from standard stereo equipment for the recording and reproducing stereophonic sound, it would be advantageous to provide an inexpensive and simple apparatus which can record and reproduce truly steroeophonic audio signals while using the monoral audio head of a VTR.
Various approaches to the so-called multiplexing of signals is known. See for example, U.S. Pat. No. 3,375,329 to Prouty relating to the quadrophonic recording of sounds by sequentially sampling, at ultrasonic frequency, the audio output from a receiver.
U.S. Pat. Nos. 3,211,841 and 3,248,718 to Uemura et al discloses apparatus for processing plural signal outputs using a single magnetic head. This system utilizes pulse width modulation which requires a demodulation process utilizing average detection.
Another relevant reference to the present invention is U.S. Pat. No. 4,139,868 to Eisenberg which employs control pulses produced from vertical sync. pulses of the video signal to multiplex a video signal. Pulses at a very low rate of about 60 Hz are utilized for this slow rate multiplexing.